1. Field of the Invention
The present invention relates to a color conversion apparatus and a color conversion method, and more particularly to a color conversion apparatus and a color conversion method for image information read by using a scanner.
2. Description of the Related Art
As the processing function of an image input device, color reproduction suitable for display on the display is performed by correcting the RGB signal (hereinafter, called “dRGB”) of a device which is read (refer to Japanese Patent Laid-Open No. 10-070665 (1998)). More specifically, the processing of identifying the color of an original by in advance measuring the spectral reflectance of the original to be read, determining normalized RGB signal values for reproducing a color with a small color difference from the identified color on the display, and converting the dRGB into the normalized RGB signals is performed. Here, the normalized RGB refers to, for example, sRGB, AdobeRGB (Hereinafter, referred to as “aRGB”. Here, Adobe is a registered trademark.) and the like. The color difference means the difference in color expressed by using a distance ΔE or the like in a CIE-L*a*b* space, for example. By thus performing color conversion, the color of an original and the color displayed on a display by reading the original are made substantially the same.
Incidentally, on the occasion of printing the image which is imaged by an image pick up device such as a digital still camera as a hard copy, color gamut compression occurs no matter what printer is used to print it. This is because the reproduction space of imaged electronic data is displayed on a display by additive color mixture, but the color space in which the printed image is reproduced is reproduced by subtractive color mixture, and therefore, color gamuts which do not match with each other theoretically occur. Therefore, the printed image is generally displayed in the color gamut differing from that of the case of being displayed in an arbitrary RGB color space such as sRGB and aRGB on a display. When an image is displayed in different color gamuts in this way, color gamut compression is performed so that the respective views become close to each other. Japanese Patent Laid-Open No. 6-225130 (1994) discloses an example of such a technique. However, the image obtained by reading an image subjected to color gamut compression is intended for having a small color difference from the image subjected to color gamut compression, and therefore, when the original read by using a scanner is displayed on a display, the image cannot be decompressed to be the image before subjected to the color gamut compression. Further, when a film photo is scanned as an original, conformity with the original is considered to be of primary importance, and colors realized by making full use of the color space which can be originally displayed by the display cannot be displayed.